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Nightmotorsport Air Oil Separating Billet Valve Covers for Subaru EJ Engines

  • Mike Kojima

If you have changed plugs in your Subaru you know what a bitch it is!  Nightmotorsport has made the plug change much easier by relieving and adding this radius to the valve cover to make more room when getting the coil packs out to get to the plugs.  This makes a big difference and makes it worthwhile to get these valve covers just for this feature alone.  Just ask this guy who did a plug change at the track a few weeks ago!

The Nightmotorsport valve covers have cooling fins machined into them on the bottom where hot oil tends to accumulate.  They also look cool!

You can see the radiused edges of the valve cover and just how much more room it gives you to wiggle out the coil packs.  You can see what a difference this will make when the engine is installed in the car and the frame rail is blocking a direct shot at the coil packs.

The Nightmotorsport valve covers are a great-looking addition to Project GD STI and are also very functional.  Nightmotorsport says their valve covers eliminate the need for additional external air oil separators but Subaru engines spit so much oil that we are still going to run the IAG air-oil separator just to have super clean, oil-free blowby that will not contaminate the intake system.  We think that the Nightmotorsport valve covers will greatly help any Subaru from stock to highly modified.

Souces

Nightmotorsport

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14 comments
  1. Spec R says:
    April 27, 2022 at 5:41 pm

    I thought these were a gimmick, but just because you endorse them, Im now a believer. Thanks!

    Reply
    1. Avatar photo Mike Kojima says:
      April 28, 2022 at 10:25 am

      Initially, I thought so too but the owner of Nightmotosport came by and walked me through the features and I was very impressed with how well thought out they were, especially being a Subie owner and living through all the typical Subie issues.

      Reply
  2. sam says:
    April 28, 2022 at 1:18 pm

    Curious to see an update at some point of accumulation in the IAG AOS after a track day. Love the content as always.

    Reply
    1. Avatar photo Mike Kojima says:
      April 28, 2022 at 1:25 pm

      Well the IAG AOS continually drains back into the crankcase which is a great feature, this way no oil is going to blow out of the engine!

      Reply
  3. Bob Roberts says:
    April 29, 2022 at 12:19 am

    Wouldn’t such a part actually have the ability to free up power considering that the intake charge is no longer being contaminated with oil?

    Although, I have heard that Ferrari (and Mercedes?) were purposefully using oil consumption to make more power, although I am certain that they were tuning for the oil and using some pretty special oil additives.

    “Oil burns when it’s introduced into a gas-powered engine’s combustion chamber, which helps generate more power at the expense of, well, oil. In F1 today, fuel is heavily regulated by the FIA, but there’s a lot more flexibility with oil used. In practice, this means that teams can use certain additives to their advantage and create a more volatile fluid, helping with combustion.”

    https://www.roadandtrack.com/motorsports/a13132940/how-todays-f1-engines-can-burn-oil-to-make-more-power/

    Reply
    1. Avatar photo Mike Kojima says:
      April 29, 2022 at 11:20 pm

      Just reduce the likelihood of detonation, it’s not going to make more power, just let the engine make its intended power. Buring oil doesn’t make power, it has less BTU than fuel.

      Reply
      1. Bob Roberts says:
        May 5, 2022 at 12:33 pm

        Couldn’t you then run more aggressive timing and make your power that way? Similar to running higher octane fuel.

        I imagine that they only did it in F1 to get around the regulations. Not the way anyone would prefer to make power. Makes a mess.

        Reply
  4. John T. Jacobson says:
    May 5, 2022 at 8:53 am

    Is this item available in the 2.0 XT in my 2016 Forester? I am also curious best build for track day, (Road America Excludes 2016 Forester XT being a SUV, from running on their track, due to roll over by their experience), Brakes, Engine oil pump, oil pick up tube, oil pan, intake hosing, ect?

    Reply
  5. Justin W says:
    May 19, 2022 at 6:32 am

    So does this mean this could be installed instead of using an AOS like something like IAG AOS systems?

    Reply
    1. Avatar photo Mike Kojima says:
      May 19, 2022 at 8:45 pm

      We are still going to run an AOS on our motor with these valve covers. Night Motorsports says you dont have to.

      Reply
  6. john says:
    August 4, 2024 at 5:02 pm

    I’m curious about these valve covers. has anyone done more extensive research on them i read somewhere that they were burning more oil but i would like to hear from other ppl that have them to make a decision on them.

    Reply
    1. Avatar photo Mike Kojima says:
      August 4, 2024 at 7:59 pm

      There is no way this is going to cause an engine to burn more oil. With these the line to the AOS is dry.

      Reply
  7. Swaggin Modifieds says:
    March 12, 2025 at 11:50 pm

    Any updates on these? Im assuming you’ve put them through the ringer by now. Considering them for a 1000+hp build. Would be running them into a catch can.

    Reply
    1. Avatar photo Mike Kojima says:
      March 13, 2025 at 3:21 pm

      There isn’t really any reside making it to the AOS. Our engines has very little blowby though because it’s properly machined and assembled.

      Reply

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